Brooklyn



May 24, 1927.

c. .L FITCH TELEPHONI C SPEAKER Filed March 20, 1926 2 Sheets-Sheet 1 W. l@ A dynv B. .1 fn

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u W/RUV! f/v )Rl/ f l 1,630,119 May 24, 1927, c. JH FITCH TELEPHONIG SPEAKER Filed March 20, 1926 2 Sheets--Sheev 2 INVENTOR ATTORNEY magneti Patenzed May 24, 1927.

UNiTi-in#sTATESy PATENT oFFicE. r

CLYDE J'. FITCH, OF BBOOLYNyNEW YORK, AASKSIGNOIR T0 C.- J'; FITCH, INC., OF f BROOKLYN, NEW YORK, A CORPORATION OF NEW YORK.

rvApplication filed March 20, l1928. Serial \No.,,96,153. s

`This invention relatesito the class of teleyphonic apparatus ordinarilygknown as loud speakers.

Special objects of Vthe invention are to improveV and simplify apparatus of` this general class, particularly. as regards the vactuating instrumentality or so-called' telephone unit. rthe tympanum or member by which thek electrical variations are converted into sound vibrations rand the mounting or assembly of these parts in a practical desirable form.` t

Theforegoing and other objects kare attained by certainnovel features of construction.- combinations and relations of parts asv hereinafter set forth. n y

In the drawings accompanying and torining part of this specification, different pref ferred embodiments of the invention are illustrated and it is tobe understood that the 'structure may be further modified without ,Y yFigure 3- is an enlarged broken sectional view illustrating particularly details in the mounting yot the flexible cone and the attachment of the cone to the armature of the yFigure 4f. is a vertical sectional view of a smaller form of the invention7 involving slight modifications. Y

Figure 5 5-5 of Figure 4.

Figure 6 is an enlarged broken sectional detail of a moditied form of armature structure. Y

Figure 7 is a broken diagrammatic repre sentation illustrating the magnetic losses occurring when the magnetic gap is locatedA outside the. coil, and ,n K

Figure 8A is aY similar view showing how this loss is prevented and the flux is obliged to cross the gap when the gap is located' within the coil,

. In the several illustrations, thetympanuin or sound i'epioducer is in the form ot acone 1. ln the first form of the invention shown, Figures 1 to 37. this cone is of fairly large size. say three feet or more in `diameter and this fact makes it practical to-combine the is ajsectional view as on linel sound. possibly in cone with a table or cabinet structure. This table is shown as made up of four corner posts 2 connected at the endsby panels 3 'andsupporting a table top 4 and an inside bottom shelf 5. This construction leaves the front and back ofthe cabinet entirely open for soundpropagation and provides a trameffor'the cone, which is mounted within the cabinet v.over th-e open ,front thereof and arranged with theapeX of the 'same yto therear. t

The coney is shown madey with a rearwardlyangled rim flange 6 .and a simple convenient and ypractical method of positioning the cone is to glue or otherwise secure turned back flaps of this flange yto the under side `the vtable top at 7, the top ofthe'y Shel-jt at 8 and the inner sides of the posts at 9. These four points of yconnection at top, bottom and sides position and partially support the conewithout hampering its sound producing vibrations.

The operating unit is shown asmounted on a bar 10extending across the open back 'of the cabinet between the corner posts at a level substantially corresponding to the apex of the cone'. i n

The construction described provides a table of general utility but particularly adaptable as a support for a radio receiving set, indicated at 11, with which the device is used and a. compartment over the bottom shelf at the back of the cone for thebatteriesV or other accessories 12 of the system. The open front and rear of the cabinet a1- low full propagation of sound waves at both sides-of the cone and the closed ends of the cabinet appear to aid propagation ofthe gle straight bar magnetk 15. LThis bar magnet in the illustration carries at one end a rigid polar projectionlt, provided by 'an angled bracket of softiron; whose base 17 is secured flat against the end portion of theI the capacity 'of soundbar by screws 1S, 19. Secured to the opposite end of the bar by screw there is shown a soft iron bracket piece 21 angled away from the bar and having attached to its upper otset end portion, a soft iron strip 2:2, having` its upper end angled toward the rigid polar projection to forin a companion polar extension 23. The strip 22 is sutliciently flexible to operate actually as an arlnature for the rigid polar projection 16.

The arinature strip 22 is shown rigidly secured at its lower end to the lower polar projection 21 by a screw and nut at 24 and as rigidly secured to the ripper end of the saine projection by the nuts Q5 on the eX- tended portion of the screw bolt 19. This bolt is preferably of noninagnetic niaterial so as notto short-circuit any of the inagnetic finzi across the gap 26 between the polar projections 16, Q3 but the screws and nuts at 18, 20, Q4 may be and preferably are of magnetic material so as tO preserve the full magnetic cross section at these points.

It will be observed vthat in addition to securing' the arinature strip rigidly to the end of the lower polar projection 2l, the nuts 25 may be adjusted one way or the other on the bolt 19 so as to shift the bracket and the arinature which it carries to increase or reduce the width yof the gap at Q6.

The opposed polar projections 16 and Q3,

the. first of which is rigid and immovable and the second of which is flexibly supported and so may be regarded as an armature. are surrounded b v an actuating` or control coil 27. This coil is shown formed with an open ccnter so as to provide av free operating space 28 for the movable armature and the coil is shown as positioned to enable this result by being supported on the rigid polar projection over an insulating bushing` 29.

To securethe full etcct of thc electrornag'net, the polar projection which forms the armature .is preferably connected with the cone by a director substantially straight line connection. rthis connection is shown as a transmission link 30 engaged at one end directly with the end of the arinature and at its opposite end with the apex of the cone.

In Figure 3 the transmission link is illustrated as a sinall stiff rod screwed at 31 into the elbow at the end of the arinature and screw threaded at its opposite end to receive the nuts 32, 33, clamping' the cone bctween thein. A small inetal washer 34 is shown engaged over the outside of the cone and over this a larger paper or like washer 35 glued or otherwise secured to the outer surface of the cone. Both the sinall metal washer and the larger paper washer are dished to tit the angle of the cone and siinilarly, the outer and inner securing nuts 39., 33 are indicated as concavely and convexly conical' to titI and closely grip the parts clamped between thein. The parts desaine is shown niounted on the bat u 'cross strap 37 caught beney scribed may be connected by riveting or soldering if desired, but the screw connections are preferred because of manufacturing and assembling advantages.

By actuating the cone or sound reproducing inediuin directly froin the free end of the armature, the full operation of the unit is utilized and hence the inaxin'nun effect is obtained. This effect may be modified or reduced, however, very readily, if that is desired, by connecting` the transmission link with the flexible portion of the elbow strip at a point more or less removed troni the el` bow at the end of the armature extension, the reduction in inoveinent increasing as the point of connection approaches the lined point represented by the clainp nuts Q5.

Structurally, it will be seen that the invention is siinple, practical and inexpensive, the operation is direct, positive, powerful and can be readily djusted; the ttable-cabinet forni of the device in addition to the superior accoustic advantages, is of an attractive, ornamental nature and pailicularljv useful because. of its sujiportingv and housing characteristics for the receiving set and its accessories. To Yposition the batteries or other accessories and prevent theni freni coininp into Contact with the back of the conc, suitable positioning` stops inay be provided on the supporting' shelf, as indicated at 36 in Figure 2.

The location ofthe magnetic gap within the coil concentrates the ilux and prevents or reduces leakage. This provides a partici".- larly powerful unit, especially' etfective for cone and like rcproducers operating' in free air-that is, without a sound bei; or horn or the like. A large con-c such as illustrated requires but comparatively sinall i'novcnieit. The unit shown particularlysuited to s because the support for the armature,though flexible, is relatively stiff and the is quite sniall. The action of the unit, therefore, quite powerful but the actual range of nieve nient is sn'iall and suited to the direc'V ctn-a.- tion of a large cone without the intei'position of any niotion reducing connections. This forni of armature also/is suited to wholly supportingthe cone.

To support the operating` unit yieldinfsv'lf,v so that there may be no' reaction fro-ni the saine which inight have a tcntency to set up vibrations in the console o cabinet, the

`th thn head prothe screw bolt 19, the endeI of said strap A jeeting far enough and being sutticier flexible and resilient to absorb vibrations from the back of the permanent magnet. These spring` supporting; arins be engaged by anysuitable securiia; leans .such as the supporting screws indicated at 38.

rlhe operatingl unit is such sturdy construction that it may be relied upon llt) `tirely support the cone, particularly the end of said magnet,a rigid magnetic bracket smaller size cones. If desired, however, they edge of the cone may be allowed to rest against a ring of telt'or the like, as indicated at 39, F igure 4. This felt ring is shown as carried by a circular trame 4() Which may form part ot' the front oi the cabinet.

The ysmall met-al Washer 34 which is engaged over the outside ot the cone terms a substantially rigid element for'the anchorage of the transmission link and the larger paper Washery 35 which is glued over the metal Washer and over the back ot' the cone Serves both as a means for securing the metal Washer to the cone and as a means Yfor bracing and stiflening the central portion of the cone. The metal cone, furt-liermore, acts inthe nature of a cup or seat for supporting the cone.

It desired, the armature may be formed as an element separate from the resilient supporting strip, as indicated at 23 in Fig i ure'6 and this construction permits et the transmission link being utilized as a fastening for securing the parts together, it being shown as having its threaded inner end eX- tending freely through an opening in the resilient supporting strip 22 and into a scren seati4lin theend of the armature member, a cross seat 42 formed in the supporting strip preventing the armature block from twisting under the action of screwing the transmission rod thereinto.

What is claimed is:

l. In combination, a permanent bar magnet, a polarprojectio'n extending from one secured to theopposite end ot said bar magnet, a yieldable magnetic strip secured to said rigid bracket and having a polar pro jection opposed to the tiret polar projection, a magnet winding associated with said polar projections and a sound reproducingmember connected with the flexibly supported polar projection. ,n

2. In combination, a permanent bar mag nelt, a polar projection extei'lding troni one end of said magnet, a rigid magnetic bracket secured to the opposite end oit said bar magnet, a yieldable magnetic strip secured to said rigid bracket and having a polar1 projection'opposed to the lirst polarprojection, a magnet windingr associated with said polar projections and a sound reproducing member connected with the flexibly supported polar projection, saidmagnct Windino` being hollow and supported by being` engaged at one end over the lirst polar projection, the opposite open end of said magnet 'freely rcceiving the flexibly supported polar projection. v

3. In apparatus oit the character disclosed, a permane-nt magnet havingl a lined polar projection, a flexible magnetic strip magnetically connected with the opposite pole of said magnet and having an angularly bent end portion projectingtoivard the fixed polar projection to form an armature therefor, a transmission link conn cted with said armature substantially at the bend mentioned,

a sound reproducing member engaged by` a permanent bar magnet having a polar elei ment at one end, a polar extension otless cross lsectional area than the bar magnet extending from the opposite end `ot said magnet toward said firstmentioned end and a resilient member ot less cross sectional area than said extension forming a continuation of said extension and carrying a polar elenient opposed to said tiret polarelement. n

tir-l. telephonie speaker unit comprising 'L rrmanently magnetizedL substantially straight magnet bar, a bracket ot magnetic material having angularly related sides,y one side being secured to one endy ofthe bar as a base and the other side projecting angularly trom the end or" the bar a polar entension, a second magnetic bracket, said second bracket having one end secured to the oppcsite end ot the magnet bar and extending therefrom in offset relation toward the iirst mentioned end of the bar, a polar extension at the other end ot' said second bracket projec'ting angularly toward the polar eXtension oi the tiret bracket, a vibration transmission connection engaged with said second polar extension and a magnet `Winding. associated with the polar extensions. n

7. AV telephonie speaker unit` compris ing a permanently magnetized substantially straight magnet bar, a bracket ot magnetic material. having angularly related sides,one side being secured to one end ot' the bar as a base and the other side projecting angularly from the end oit the bar as a polar e); tension.l a second magnetic bracket, said second bracket having on-e end secured to the opposite end ot the magnet bar and extending therefrom. in offset relation toward the icc first mentioned end ot the bar, a polar extension at the other end ot said second bracket projecting` angularly toward the polar extension of the lirst bracket, a vibra- `offset portion of the second bracket from the bar to regulate the magnetic gap betiveen lil the polar extensions within the magnet winding.

8. A telephonie speaker unit comprising a permanently magnetised substantially straight magnet bar, a bracket of magnetic material having angularly related sides,'one side being secnred to one end et the bar as a base and the other side projecting angularly from the end ot the bar as a polar extension, a second magnetic bracket, said second bracket haring one end secured to the opposite end et the magnetbar and extending therefrom in otliset relation toward the `first mentioned end or the bar, a polar' extension at the other end ot said second bracket projecting angularly toward the polareirtensien ot the lirst bracket, a Vibration transmission connection engaged with said second polar extension and a magnet winding associated with the polar extensions and screw means tor variably spacing the offset portion et the second biacket in relation to the bar to regulate the gap between the polar extensions.

9. A telephonie speaker unit coniprising a permanently magnetized ff-:ubstaiitially straight magnet bar, a bracket et magnetic material having angularly related sides, one side being secured to one end ot the bar as a base and the other side projecting angularly from the end ot the bar as a polar extension, a second magnetic bracket, said second bracket having one end secured to the opposite end et the magnet bar and extending therefrom in offset relation toward the first mentioned end ot the bar, a polar eX- tension at the other end et said second bracket projecting angularl)T toward the polar extension of the tirst bracket, a vibration transmission connection engaged with said second polar extension and a magnet winding associated with the polar extensions, the base ot the tirst bracket being secured to the bar by a screw stud and said screw stud being engaged with the otlsct portion oi" the second bracket to position the same relative to the bai.

l0. A telephonie speaker unit coniprising a permanent-ly inagnetized substantially straight magnet bar, a bracket et magnetic material having angularly rrelated sides, one side being secured to one end et the bar as a base and the other side project-ing' angulai-ly from the end et the bar as a polar extension, a second magnetic bracket, said second bracket haring one end secured to the opposite end ot the magnet baiI and extending therefrom iii oti'set relation toward the lirst mentioned end et the bar, al polar extension at the other end et said second bracket projecting angularly toward the polar extension ot the tirst bracket, a T,'bratien transmission connection engaged withA said second polar extension and a magnet windin` associated with the olar exteni D sions, cured the base oit the lirstbracket being seto the bar by a screw stud and said screw stud being engaged with the offset portion ot the second bracket to 'position the same 'relative to the bar and a mounting strap for the unit held to the bar by said same screw stuc.

ll. A telephonie speaker unit comprising apermanently magnetized substantially straight magnet bar, bracket oi magnetic material haring angularly related sides, one side being secured to enfl end et the bar as a base ane the other side projecting alignlarly treni the end ot the bar as a polar eirtension, a second magnetic bracket, said second bracket having one end secured to the opposite end el the magnet bar and extending therefrom in otlset relation toward the tirst mentioned end ot the bar, a polar eX- tensien at the other end et said second bracket projecting angularly toward the polar extension oitI the lirst bracket,a vibration transmission connection engaged with said second polar extension and a magnet winding associated with the polar extensions, the base et the lirst bracket being secured te the bar by a screw stud .and said screw stud being engaged with the olf-set vportion oli' the second bracket to position the same relative to the bar and a mounting strap for the unit held to the bai by said same screw stud, the second polar extension being a separate strip held to the ottset. portion et the second bracket by said same screw stud.

1Q. A telephonie speaker unit comprising a permanently magnetized substantially straight magnet bar, a bracket ot magnetic material haring angularly related sides, one side being secured to one end of the bar as a base and the other side projecting angularly trom the end ot the bar as a polar extension. a second magnetic bracket, said second bracket having one end secured to the opposite end ot the magnet bar and extending therefrom in otlset relation toward the lirst mentioned end ot' the bar, a polar extension at the other end et lsaid second bracket prej ecting angularly toward the polar extension ot the lirst bracket, a vibration transmission connection engaged with said second polar extension and a magnet winding associated with the polar extensions, said second polar extension being a separate flexible strip secured to the ol'l'set portion ot' the second bracket. i

13. A. telephonie speaker unit comprising a permanently magnetized substantially straight magnet bar, a bracket ot magnetic material having angularly related sides, one side being secured to one end et vthe bar as a base and the other side projecting angularly from the end of the bar as a polar eX- tension, a second magnetic bracket said second bracket having one end secured to the opnoslte end ot the magnet bar and extend- CII said second polar extension and a magnet Winding associated with the polar extensions, 'said second polar extension being separate'flexible strip secured to the offset portion ot' the second bracket and` said oiiset portion being rigidly secured tothe bar in spaced relation and the flexible strip projecting freely beyond sach rigidly held portion.

14. A telephonier speaker unit coiiiprsing a permanently magnetized substantially straight magnet bar, a bracket of magnetic material having angular-ly relatedy sides, one side being secured to one end ot the bar as a base and the other vside projecting angularly from the end of the bar as a polar ei;- tension, a second magnetic bracket, said. second bracket having one end secured to the opposite end of the magnet bar and extending therefrom in offset relation toward the'. first mentioned end of the bar, a polar eX- tension at the other end of said second bracket projecting angularly toward the polar extension of the lirst bracket, avibrationv transmission connection engaged 'with said second polar extension and a magnet Winding associated with the polar extensions, the base ot' the iirst bracket beingsecured to the bar by a screiv stud and said screw stud being'engaged with the oiiset portion of the second bracket to position the same relative to the bar, 'said screw stud beingof non-magnetic material and having Lof said legs, a magnet Winding associated With said polar projections and a strut connecting the legs ot' the yoke, said strut having means of adjustment enabling variations in the relation of the non-permanent to the permanent magnet leg.

16. A telephonie speaker unit comprising separately formed legs rigidly secured together at one end and spaced at their opposite ends to constitute a magnet yoke, one of said legs being a permanent magnet and the other being only of magnetizable material,

opposed polar projections at the ends of said legs, a magnet Winding associated with said polar projections and a strut connecting the legs oit the yoke, said strut having means of adjustment enabling variations in the relation of the non-permanent to the permanent magnet leg and the polar projection of one ol the legs being flexible beyond said strut.

17. A telephonie speaker unit comprising a permanently ii'iagnetized magnet bar, a pole piece at one end of ysaid bar, a rigid magnetic bracket secured to the opposite end said bracket rigidly spaced `from the body of the bar. a yieldable magnetic strip secuied to .said rigidly held bracket and yprojecting beyond said strut, a polar projection carried by said projecting portion of the yieldable strip in opposition to the pole piece of the bar and a magnet Winding associated With said pole piece. n

18. A telephonie speaker unit comprising a permanently magnetized magnet bar, a pole piece at one end of said bar, a rigid magnetic bracket secured to the opposite end of said bar, a strut securing the free end of said bracket rigidly spaced from the body ofthe bar, a yieldable magnetic stripl secured. to said rigidly held bracket and projecting beyond said strut, a polar projection carried by said projectingportion of the yieldable strip in opposition to the pole pieceoi" the bai and a magnet `Winding associated with said pole piece, said strut also securing saidstrip to the bracket and havingr means enabling adjustment of the two relative Ato the magnet ban 19. Atelephonic vspeaker unit comprising a permanently inagnetized substantially straight magnet bar, brackets of magnetic material having base portions secured in flat engageiiient with the same side of said bar. at opposite ends of the same, said brackets being angled away 'fronisaid side of the Aloar and provided with opposed pole pieces faid bar, a strutsecuring the tree end of cek 

